I have been using Ubuntu for a long time as my primary operating system. It is easy to install, stable and it uses the fantastic apt-get from Debian. In my opinion, it is a good choice when you're getting starting on Linux World or if you want to use Linux as a Desktop/User station.
If you want to setup a server machine, my advice is to
test Slackware ou debian. (I'm get used with Slackware for servers)
Regards, Jair Rillo Junior
http://www.jairrillo.com/blog, SCJA 1.0, SCJP 1.4, SCWCD 1.4, SCBCD 5.0, IBM SOA Associate (Test 664).